1. Field of the Invention
Embodiments of the present invention relate generally to coded aperture optics, systems, and methods operable with and pertaining to focusable radiation and, more particularly, to an optical element for generating a band-limited uniformly redundant array (bl-URA) from light within a spectrum of focusable radiation, an optical imaging device incorporating the optical element, and a method for determining a transmission function P(ξ, η) for an optical element that will generate a desired intensity pattern A(x,y) on a detector from light within a spectrum of focusable radiation from a point on an object.
2. Technical Background
Conventional refractive and reflective optical components (e.g., lenses, mirrors) are not useful for imaging nonfocusable radiation such as, e.g., γ-rays and X-rays. The comparatively shorter wavelengths simply do not refract in the more suitable manner of comparatively longer wavelengths in, e.g., the visible spectrum. However, a simple pinhole camera can be used as an imaging device for γ-rays and X-rays because diffraction effects are minimal, in contrast to those effects in the UV to sub-millimeter and, particularly the visible, regime, which cannot be ignored.
The concept of using a coded aperture to image nonfocusable radiation was first introduced by L. Mertz and N. Young, Proc. Conf. Optical Instruments and Techniques, London 1961, p. 305 and later implemented with random arrays by R. H. Dicke, Astrophys. J. 153, L 101 (1968) and J. G. Ables, Proc. Astron. Soc. Aust. 4, 172 (1968); see also U.S. Pat. No. 3,700,895). In the formulation by Dicke and Ables, the opening of a single pinhole camera was replaced by many randomly arranged pinholes collectively known as the aperture. Each point of a self-luminous object projected a shadow of the aperture on a recorded image plane (picture). Subsequent correlation processing of the picture yielded a reconstructed image that resembled the original self-luminous objects.
Uniformly redundant arrays (URAs) used for coded aperture imaging were first disclosed by Edward E. Fenimore et al. in U.S. Pat. No. 4,209,780 as well as in Applied Optics, 17, p. 337, Feb. 1, 1980, Applied Optics, 17, p. 3562, Nov. 16, 1978, Applied Optics, 18, p. 945, Apr. 1, 1979, and in Los Alamos Scientific Laboratory Mini-Review, LASL-78-102, January 1979. U.S. Pat. Nos. 4,360,797 and 4,389,633 disclose further information about coded aperture imaging.
A variety of coded aperture systems pertaining to the optical regime are reported in David P. Casasent, Timothy Clark (Ed.), Proc. SPIE 6714 (2007); David P. Casasent, Stanley Rogers (Ed.), Proc. SPIE 7096 (2008); Keith Lewis, Proc. SPIE 6714 (2007) 671402; and Tim Clark, Esko Jaska, Proc. SPIE 6714 (2007) 671403.
The inventors have recognized the many benefits and advantages realizable by a coded aperture optics operable over the focusable radiation spectrum.